Topband: Input Impedance of the FT1000/S-Meter Calibration issues

[Rick Karlquist]

> 14.0MHZ  (17+j24)  (16+j19)  (18+j21)  (10+j16)
>
> These readings illustrate the futility of trying to calibrate the
> S-meter in  absolute units, with  over 10-20 db of variation at the
> input terminals.  Another interesting note: I used an HP 4815A Vector
> 73
> Eric von Valtier K8LV

There is not 10-20 dB of variation in the S-meter.  The
worst case mismatch you show is 10+j16.  Even this 5:1
SWR only results in a 3 dB mismatch loss, still not much
in the overall scheme of things.  (You can find mismatch
loss on any decent Smith chart).

Also, you can easily fix even this 3 dB by using your
own external attenuator instead of the 6, 12, 18 dB attenuator
in the rig.  Either the attenuator in the rig is incorrectly
designed or there are severe mismatches elsewhere.  In
either case, an external attenuator will take care of it.


Rick N6RK